Safety joint for oil well drilling stems



y 0, 1955 w. N. SUTVLIFF 2,708,100

SAFETY JOINT FOR OIL WELL DRILLING STEMS Filed June 1, 1951 IN V EN TOR.[dam/.5 M fun/FF ATTOP/VEYS United Sttes Patent SAFETY JOKNT FOR 011.WELL DRILLING STEMS Wayne N. Sutliff, Bakersfield, Calif.

Application June 1, 1951, Serial No. 229,388

4 Claims. (Cl. 255-28) The present invention relates to well devices,and more particularly to a safety joint construction adapted to beincorporated in a tubular string disposed in the well bore, for thepurpose of elfecting disconnection between portions of the tubularstring in the event the latter becomes stuck in the well bore.

An object of the present invention is to provide an improved safetyjoint for a tubular well string capable of safely supporting andtransmitting heavy loads, and of readily being released whenever desiredunder the control of the operator.

Another object of the invention is to provide a safety joint whichcannot be released inadvertently during normal rotation of the tubularstring attached to the safety joint, and which is capable of striking ajarring blow to release the joint whenever such release is desired bythe operator.

A further object of the invention is to provide a safety joint whichcannot be released so long as a pendent load is being supported on thejoint, which is the normal condition encountered in well bores wheneverthe tubular string attached to the joint is in tension.

Yet another object of the invention is to prevent release of a safetyjoint unless the upper portion of the joint is first moved downwardlywith respect to the lower portion.

This invention possesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of a formin which it may be embodied. This form is shown in the drawingsaccompanying and forming part of the present specification. It will nowbe described in detail, for the purpose of illustrating the generalprinciples of the invention; but it is to be understood that suchdetailed description is not to be taken in a limiting sense, since thescope of the invention is best defined by the appended claims.

Referring to the dawings:

Figure 1 is a longitudinal section, with parts shown in side elevation,through a safety joint, disclosed as forming part of a string of drillpipe, the parts being arranged for normal rotation of the string;

Fig. 2 is a longitudinal section through a portion the safety jointillustrated in Fig. 1;

Fig. 3 is a view similar to Fig. 2, with the parts arranged foreifecting release of the safety joint;

Fig. 4 is a cross-section taken along the line 44 on Fig. 1;

Fig. 5 is a cross-section taken along the line 5---5 on Fi 1;

Fig. 6 is a cross-section taken along the line 6-6 on Fig. 2, throughthe jarring portion of the safety joint, and with the parts in theirnormal relationship;

Fig. 7 is a view similar to Fig. 6, in which the jarring mechanism hasbeen reversely rotated to a position of initial impact between thedriving lug and driven lug.

Fig. 8 is a view similar to Fig. 7, showing the driven lug as havingbeen moved to thereby partially unthread the collar.

Fig. 9 is a view similar to Fig. 5, showing the safety joint partiallyunthreaded.

The safety joint A disclosed in the drawings is adapted to connect upperand lower portions B, C of a tubular string in spaced relation. Thus,the joint includes an elongate tubular body 10 having a lower pin 11threaded into the upper box portion of a lower joint of tubing for drillpipe C. The upper mandrel 12 of the joint is suitably secured to anupper joint of tubing or drill pipe ,B, which forms part of an uppertubular string portion running to the top of the well bore.

The tubular mandrel 12 is telescoped within the tubular body 10 and hasan external groove 13 on its lower cylindrical portion for containing asuitable seal 14, such as a rubber, or rubber-like, O ring adapted toslidably seal against the cylindrical wall 15 of the tubular body. Aboveits cylindrical sealing surface, the body has an enlarged diameterportion 16 extending upwardly from a shoulder 17 to a plurality ofinternal splines or keys 18 that are adapted to be engaged by companionexternal splines or keys 19 formed on the lower portion of the mandrel12. When the mandrel splines 19 are fully engaged with the internal bodysplines 18, the lower end of the mandrel keys 19 are disposed asubstantial distance above the body shoulder 17 forming the lower end ofits enlarged diameter portion 16.

The mandrel 12 is urged upwardly with respect to the body 10 by ahelical compression spring 20 disposed in the cylindrical body bore, thelower end of the spring bearing upon a lower body shoulder 21 and theupper end against the lower end of the mandrel 12. This spring may exerta substantial upward force on the mandrel 12, maintaining a shoulder 22on the mandrel and above its keys 19 in engagement with the lower end ofa stop collar 23 that is detachably secured to the upper end of the body10 by means of external threads 24 on the collar meshing with companioninternal threads 25 at the upper portion of the body 10 and above itsinternal splines 13. The threaded connection 24,

\ 25 disclosed is right-hand and the extent of threaded movement of thestop collar 23 into the body is determined by engagement of an inclinedshoulder 26 on the stop collar immediately above its threaded portionwith a companion inclined upper end 10a of the body. Unscrewing of thecollar 23 from the body 10 is normally prevented by one or morefrangible elements 27, in the form of one or more pins extendinglaterally through the body and into the collar, as disclosed mostclearly in Figs. 1 and 5.

When the splines 18, 19 are in engagement with each other, the mandrel12 and body 10 cannot rotate with respect to one another. However, uponlowering of the mandrel 12 within the body 10 against the force of thecompression spring 20, the external splines 19 can be disposed in thecircumferentially continuous annular space 28 in the body 10, which thenallows the mandrel to be rotated relative to the body to a limitedextent. The limitations of such relative rotation are determined by anexternal driving projection or key 29 on the mandrel 12 which isengageable with an inwardly directed driving projection or key 30 formedin the collar 23 and extending longitudinally therealong. The externaland internal projections 29, 30 only extend a relatively small arcuateextent around the circumference of the mandrel and col-- lar, to allowthe mandrel to rotate relatively within the collar. to a substantialextent. As disclosed in the drawings, the mandrel 12 can rotateapproximately 300 degrees within the collar 23.

Assuming that the safety joint A forms part of a string of drill pipeused in rotating a drill bit (not shown) at the bottom of the well bore,the drilling string normally is in tension, with the safety joint partsarranged as disclosed in Figs. 1, 2 and 5. That is, the driving mandrelsplines 19 are in full bearing engagement with the companion bodysplines 18, the load of the lower portion of the drill string C beingtransmitted to the mandrel 12 through the threaded safety jointconnection 24, 25', stop collar 23 and mandrel shoulder 22'. Asdisclosed, the jar projection 29 on the mandrel is adjacent one radialface 301) of the companion jar projection 30 on the stop collar 23.Drilling fluid can be pumped down through the tubular string B, safetyjoint mandrel 12 and tubr body it) for continued passage through theother drill pipe joints C to the drill bit, in the usual manner, leakagethrough the joint being prevented by the sealing engagement of the Oring 14 with the cylindrical surface 15 of the tubular body 10'.

Inasmuch as the splines 18, 19' are in engagement with one anotherduring transmission of the drill .g torque between the mandrel 12 andbody 10, no turning effort or torque is imposed on the threaded stopcollar 23, which is positively prevented from being unscrewed from thetubular body it) by the frangible pin connection 27.

In the event the drill bit or drill pipe C below the safety joint Abecomes stuck in the hole, the safety joint can be released to removethe upper portion B of the drill string from the well bore. To releasethe joint, the drill string is rotated in a counter-clockwise directionto an extent sutficient to twist the upper portion B of the drill pipestring and impose a torsional, spring-like characteristic therein andyet to an extent insufficient to unthread the sections of drill pipefrom one another. the drill string being held at the surface, the upperportion 8 is lowered relative to the lower stuck portion C until themandrel splines 19 clear the internal body splines 18, whereupon thelower part of portion B of the drill string, including mandrel 12,rapidly unwinds in a counter-clockwise direction, causing the drivinglug 29 to strike a sharp blow against face 30a of the driven lug 3%) ofcollar 23 (see Fig. 7), moving the driven lug 39 and therefore collar 23from the position shown in Fig. 7 to the position shown in Fig. 8,shearing pin 27 and at least partially unscrewing collar 23 from thetubular body 10 (see Fig. 9). The position shown in Fig. 8 is merelyapproximate and the collar may unthread somewhat more or less indifferent releasing operations. Once the safety joint is broken, in themanner described above, the upper portion of the tubular string B can berotated to the left, the driving lug 29 engaging the driven lug 30 untilthe collar 23 is completely unscrewed from the threaded box 25,whereupon the drill pipe string B can be elevated to elevate the mandrel12 from the body 10, the mandrel shoulder 22 5 engaging the lower end ofthe collar 23 and lifting it with it. The mandrel l2 and collar 23 canthen be removed to the top of the well bore.

Although described specifically in connection with a drill string, thesafety joint can be used in connection with other strings, such asfishing strings, and sucker rod strings.

It is, accordingly, apparent that a safety joint has been provided whichcannot be released inadvertently during the normal transmission oftorque therethrough, and with a pendant load supported from the lowerportion 10 of the joint. The safety joint can only be broken ordisconnected purposely upon downward telescoping of its upper portion 12within its lower portion 10.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. A safety joint for connecting sections of a runningin string forintroduction into a well bore comprising upper and lower joint membersarranged to be secured to upper and lower sections of the stringrespectively, said members having end portions interengageable intelescoping relation, means upon said end portions normally Then, withpreventing relative rotation of the joint members and disengageable byrelative axial movement to permit such relative rotation, a collarconnecting the coupling members, said collar being threaded onto onecoupling member and having limited axial and rotative movement relativeto the other coupling member, and driving and driven lugs upon thecollar and said other coupling member, the driving lug being movablecircumferentially within the collar to impart jarring impact against thedriven lug by torque developed in the string for unscrewing the collarfrom the coupling.

2. A safety joint for connecting sections of a runningin string forintroduction into a well bore comprising upper and lower joint membersarranged to be secured to upper and lower sections of the stringrespectively, said members having end portions interengageable intelescoping relation, means upon said end portions normally preventingrelative rotation of the joint members and disengageable by relativeaxial movement to permit such relative rotation, a collar connecting thecoupling members, said collar being threaded onto one coupling memberand having limited axial and rotative movement relative to the othercoupling member, and driving and driven lugs upon the collar and saidother coupling member, said driving lug being movable circumferentiallywithin the collar to impart jarring impact against the driven lug bytorque developed in the string for unscrewing the collar from thecoupling, and a shear pin normally securing the collar against rotationand severable by the jarring impact of the driving and driven lugs.

3. A safety joint for connecting sections of a string to be run into awell bore comprising a pair of telescoping coupling members attached tothe sections for connecting the same, means upon the members normallyinterengageable to prevent relative rotation of said members anddisengageable by relative axial movement of the members to permit suchrotation, spring means normally holding the coupling members in theirinterlocked relation; a collar slidably and rotatably connected to onemember and threaded onto the other member for limiting relative axialmovement of the members, and lugs upon the collar and one of thecoupling members operable by torque developed in the strings to impartjarring impact to the collar for unscrewing the collar from the couplingmember when the coupling members are moved axially into their rotatablerelation.

4. A safety joint for connecting sections of a string to be run into awell bore comprising a pair of telescoping coupling members attached tothe sections for connecting the same, means upon the membersinterengageable to prevent relative rotation of said members anddisengageable by relative axial movement of the members to permit suchrotation, spring means normally urging the coupling members into theirinterlocked relation, :1 collar engaging the upper coupling member andthreaded into the lower coupling member and provided with shouldersengaging the coupling members for limiting relative axial movementthereof, a drive lug upon the upper coupling member, a driven lug uponthe collar, the drive lug being movable circumferentially within thecollar for imparting jarring impact to the driven lug when the couplingmembers are moved axially into relative rotatable relation, and a shearpin normally securing the collar to the lower coupling member, said pinbeing severable by jarring impact of the drive lug against the drivenlug.

References Cited in the file of this patent UNITED STATES PATENTS2,039,943 Wicket-sham et a1. May 5, 1936 2,039,945 Wickersham et al. May5, 1936 2,565,547 Collins Aug. 28, 1951

